const fn = (arr) => arr.map(item => item+1);
let obj = Object.assign({},{YY: 999});
// let PRX = new Proxy(obj, {  // 测试显示 polyfill  没有Proxy
//   set(key,val) {
//     obj[key] = val
//   },
//   get(key) {
//     return obj[key]
//   }
// })
// console.log(fn([1,2,3]),"fnnn::::",obj,"obj:::",PRX, "PRX");

window.onload = () => {
  const aq = fn([1,2,3]).toString();
  const bq = obj.toString();
  document.write(`a:::::${aq}b:::::::${bq}c::::::${bq}`)
}